In the practice of reflectometry, ellipsometry, polarimetry and the like, it is critically important to know the precise angle (AOI), and plane (POI), of incidence at which a beam of electromagnetic radiation is caused to impinge upon said sample to allow accurate determination of values of sample characterizing parameters, such as the PSI and DELTA thereof. Further, it is noted that the (AOI) and (POI) can change with location on a sample surface as the result of said surface being uneven, thereby requiring alignment at each location of a sample surface investigated.
Examples of systems which are applicable to effecting sample alignment are disclosed in, for example, Patents to Liphardt or Liphardt et al. U.S. Pat. Nos. 7,084,978; 7,230,699; 7,304,792; 7,304,737 and 7,277,171. In general, prior art systems provide means for adjusting the orientation of a sample to cause a known, precise angle (AOI) and plane (POI) of incidence. It is noted that sample alignment systems generally utilize a sample supporting stage which is rotatable about axes in the plane of a sample surface, the position of which along a locus normal to the plane, of the sample surface, can also be adjusted.
It is also noted that CD players utilize a technique of applying a laser beam to read information therein, via a Cylindrical lens, and detect the shape of a beam reflected from the CD to determine appropriate head reading “height”. Patents relevant to CD Head Height are U.S. Pat. No. 5,187,617 to Kaminaga; U.S. Pat. No. 5,003,406 to Hatananka et al; U.S. Pat. No. 4,935,827 to Oldershaw et al.; U.S. Pat. No. 4,916,555 to Hathaway et al.; U.S. Pat. No. 4,825,311 to Saito; U.S. Pat. No. 4,800,447 to Toba; and U.S. Pat. No. 4,531,162 to Tokumitsu. Known Published Applications are US2004/0179288 by Kagami et al. and US2004/0117811 by Furuya et al. Additional known Patents are U.S. Pat. Nos. 5,218,415; 4,595,829; 5,136,149; 6,091,499; 3,880,524; 4,558,949; 4,589,773; 6,504,608; 6,930,765; 4,357,696; 4,006,293; 6,734,967; 4,503,324; EP1114979A1; and EP950881A2.
What is not disclosed or fairly suggested in prior art is a method of sample alignment which enables aligning Z-height and tip/tilt with a single system that uses astigmatism to sense Z-height and beam position to sense tip/tilt. The prior art describes using astigmatism in sample alignment, but teaches away from the present invention by requiring the focusing of a beam of electromagnetism involved, onto the sample being aligned.
It is also noted that most known prior art systems utilize a beam oriented at an oblique angle of incidence to a sample to determine sample alignment.
In view of the prior art it should be appreciated that a system and method of its use that would allow alignment of a sample by monitoring, (eg. directly observing a video monitor output), the location of, and geometric attributes of an intercepted pattern formed by reflection of an electromagnetic beam, which is directed to be incident onto said sample along a locus which is substantially normal to said sample, while altering the orientation and/or “Z” position of said sample while directly observing the effect of adjustments, would provide utility.